Case study:Biotop and flood measures in the Mykle river (Mykleelva) and Vanebu river (Vanebuelva)

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Location: 59° 24' 1", 9° 42' 5"
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Project overview

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Status Complete
Project web site
Themes Environmental flows and water resources, Flood risk management, Habitat and biodiversity, Hydropower, Hydromorphology
Country Norway
Main contact forename Steinar
Main contact surname Bergan Tronhus
Main contact user ID
Contact organisation Water District (Vannområde) Siljan - Farris
Contact organisation web site http://
Partner organisations Skagerak Kraft AS, University of South-Eastern Norway (USN)
Parent multi-site project
This is a parent project
encompassing the following
Project picture

Project summary

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Mykleelva and Vanebuelva are part of the same river system, separated by two small lakes. They are regarded as heavily modified water bodies (HMWB) because the flow regime is regulated for hydropower. The reason for carrying out habitat improvements was because the water bodies have no requirements for minimum water flow. This results in very low water flows during periods of the year.

In this project, an improved thalweg (line of fastest flow and deepest water) and ponds were made at several locations along the rivers. These maintain greater habitat stability and connectivity during low flows. A new road and bridge across the river were also built as flood measures.

Monitoring surveys and results

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Lessons learnt

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It took some time for the measures to be implemented, but eventually they were carried out as planned. It will take time for the expected ecological improvements to happen. The new pool and running water areas will undergo recolonization and adaptation.

The effect of such measures can be difficult to measure, but there is little doubt that more stable water flow, larger and deeper pools and concentration of water flow will benefit the ecosystems in and around the rivers.

Thus far, the rivers have only achieved moderate ecology potential and further measures are needed to raise their ecological status further. As the water bodies are HMWBs, they will never reach full good ecological status, but with further restoration measures Mykleelva and Vanebuelva can achieve good ecological potential.

The improvement works will require maintenance as their “life expectancy” depends on the amount of river sediment transport and the frequency and magnitude of the floods.

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Catchment and subcatchment


Name Mykleelva and Vanebuelva
WFD water body codes 015-219-R and 015-328-R
WFD (national) typology REL3221
WFD water body name Mykleelva and Vanebuelva (Vanebuvann - Hogstad)
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body Yes
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present No
Species of interest Salmonids
Dominant hydrology Artificially regulated
Dominant substrate Cobble
River corridor land use Coniferous woodland (semi natural)
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)

Project background

Reach length directly affected (m)
Project started 2011/01/01
Works started
Works completed
Project completed
Total cost category
Total cost (k€) 20
20 k€
20,000 €
Benefit to cost ratio
Funding sources Skagerak Kraft AS

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance

Reasons for river restoration

Mitigation of a pressure Hydropower, Barriers to fish migration
Hydromorphology Continuity for organisms, Freshwater flow regime, Quantity & dynamics of flow
Biology Fish, Invertebrates
Other reasons for the project


Structural measures
Bank/bed modifications Creation of fish refuge areas, Construction of dams, Providing of continuity, Creation of low flow channel, Boulder restoration
Floodplain / River corridor
Planform / Channel pattern Reconnection of water bodies to the river
Non-structural measures
Management interventions
Social measures (incl. engagement)


Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Monitoring documents

Additional documents and videos

Additional links and references

Link Description Measures proposal rapport.pdf Report

Supplementary Information

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